Tractor mounted loader linkage



Feb. 27, 1968 F. J. CLARKE TRACTOR MOUNTED LOADER LINKAGE Filed Oct. 17, 1966 INVENTOR FREDERICK J. CLARKE United States Patent Office 3,370,729 Patented Feb. 27, 1968 3,370,729 TRACTOR MGUNTED LOADER LINKAGE Frederick J. Clarke, Far Rockaway, N.Y., assignor to International Harvester Company, Chicago, 111., a corporation of Delaware Filed Oct. 17, 1966, Ser. No. 587,111 7 Claims. (Cl. 214-77d) This invention relates to a loader linkage to be mounted on the forward end of a tractor for controlling bucket movement, and more particularly to a pivoted two-piece boom linkage so arranged with hydraulic operating cylinders to provide automatic self-leveling of the bucket during movement thereof.

As is well known in the art, it is desirable to maintain the bucket of a forward loader in a relatively upright position during raising and lowering of the bucket. This insures retention of a maximum load in the bucket to provide more efficient earthmoving, and gives a safer operating condition by preventing spillage from the bucket onto the tractor and operator. Also by automatically providing this self-leveling, the operator is relieved of manually maintaining a level condition of the bucket thus freeing his attention and movements for other operations.

lvVhile self-leveling is well known in the loader field, the previous self-leveling arrangements have generally been bulky and complicated, often times incorporating extra hydraulic cylinders and thereby considerably raising the cost of the equipment. Thus a primary object of this invention is to provide novel loader self-leveling linkage which is simple, relatively maintenance free, and economical to construct.

Another object of the present invention is to provide self-leveling loader linkage using only the two standard hydraulic rams, e.g., a lift ram and a tilt ram.

Still another object of the present invention is to provide a self-leveling loader linkage wherein the boom reach is extended in the raised position thereby having a more forward reach than a conventional boom.

A further object of the present invention is to provide a self-leveling loader linkage having a two pie'ce boom pivotally connected together with a plurality of engaging stop surfaces on the connected ends of each of the two boom sections to allow the rearward boom section to move from its lowermost position with one set of stops engaged, to its uppermost position; after which the forward boom section continues raising the bucket until a second set of stop surfaces are engaged to prevent further upward motion.

Other objects and advantages will become readily apparent from the following detailed description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a perspective view of the loader linkage showing the double-boom structure;

FIGURE 2 is a side view of the loader linkage connected to the forward end of a tractor, with the bucket in its lowered position, and;

FIGURE 3 is similar to FlGURE 2, but showing the bucket in its uppermost position, with an intermediate position shown in phantom.

While an illustrative embodiment of the invention is shown in the drawings and will be described in detail herein, the invention is susceptible of embodiment in many different forms and it should be understood that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawings, FIGURE 1 shows a perspective of the loader linkage attached to a tractor 19. It should be noted that the boom assembly 11 is duplicated on each side of tractor 10, however since both sides are identical only one side will be described. The boom assembly 11 includes a rear boom arm 12 and a forward boom arm 13. The rear boom arm 12 is pivotally connected at one end to the tractor 10 as at 14 and extends forwardly of the tractor. The other end of the rear boom arm 12 is pivotally connected to one end of the forward boom arm 13 as at 15. A- bucket 16 held by a bucket mounting support 17 is pivotally connected to the other end of the forward boom arm 13 as at 18.

The rear boom arm 12 includes a rear boom arm upper stop surface as at 19 and a rear boom arm lower stop surface as at 20. The forward boom arm 13 includes similar stops; namely, a forward boom arm upper stop 21 and a forward boom arm lower stop 22. The interaction of these stops 19, 20, 21, and 22 will be described in more detail hereinafter.

Two actuating devices, herein shown as hydraulic rams, are necessary to provide movement of the boom assembly 11 and the bucket 16. A lift cylinder 23 pivotally connected at one end to the forward boom arm 13, as at 24, and pivotally connected at the other end to the tractor 10, as at 25, provides the necessary power for raising and lowering the boom assembly 11, as is well known in the art. A tilt cylinder 26 provides the necessary power for moving the tilt linkage 27 to control movement of bucket 16. This tilt linkage 27 provides for self-leveling of the bucket 16 as is well known in the art of four-bar mechanisms, and includes the tilt cylinder 26, which is pivotally connected at one end to the rear boom arm 12 as at 28; and a pair of links (a first link 29 and a second link 30). These links are arranged with the first link 29 pivotally connected adjacent one end thereof to the forward boom arm as at 31 and pivotally connected adjacent the other end to one end of the second link 30 as at 32, the other end of the second link 30 being pivotally connected to the bucket 16 or bucket mounting support 17 as at 33. Thus when the tilt cylinder 26 is pivotally connected at one end to the rear boom arm 12 as at 28 and pivotally connected at the other end to a midportion of the first link 29 as at 34, the tilt linkage 27 maintains the bucket in a substantially level position as the boom assembly 11 is being moved due to the interaction of two sets of four-bar linkages having link 29 common to each set, the first set comprised of the links between the pivots 34, 28, 15, and 31; the second set comprised of the links between pivots 31, 32, 33, and 18.

A standard hydraulic circuit (not shown) is used to provide hydraulic fiuid for operating both the lift cylinder 23 and the tilt cylinder 26 as is well known in the art.

In operation, assuming the bucket 16 is in its lowermost position, hydraulic fluid is applied to lift cylinder 23 to raise the boom assembly 11 and the bucket 16. Because of the weight of bucket 16 and the load therein, the two lower stops, rear boom arm lower stop 20 and forward boom arm lower stop 22 remain engaged. It will be noted that these lower stops, 20 and 22, determine the minimum angle between the rear and forward boom arms. When the boom assembly 11 is raised to its intermediate position or any predetermined position, the rear boom arm is forced against another stop 35 (herein shown as mounted on tractor 10). This prevents further upward movement of rear boom arm 12 and as lift cylinder 23 continues to extend, the forward boom arm 13 is raised by pivoting about 15 until the rear and forward boom arm upper stops 19 and 21 become engaged. This determines the maximum angle between the rear boom arm 12 and the forward boom arm 13.

It should be noted that the distance between pivot 14 and pivot 18 is greater when the boom assembly 11 is in its raised position than when said assembly is in its lowered position. This provides a more forward reaching loader linkage than is possible with a fixed boom assembly when the bucket is raised to the maximum elevation.

When lowering the boom assembly, the lift cylinder 23 is retracted. This gives the opposite action :as is present in raising, and the forward boom arm 13 (because of the weight of the bucket 16) lowers until boom arm stops 20 and 22 again become engaged, after which the rear boom .arm 12 lowers.

Since the over-all length of the tilt cylinder 26 remains the same except when the operator desires to move the bucket 16, the tilt linkage 27 will provide for automatic self-leveling of the bucket 16 during upward and downward motion of boom assembly 11.

Accordingly a loader linkage which provides the ob jects set forth hereinabove and one which fulfills a definite need in the field of front end loaders has been shown and described.

What is claimed is:

1. A loader linkage for use with a tractor including, a boom assembly pivotally attached to the tractor at one end of the assembly, a bucket pivotally attached to the boom assembly at the other end thereof, tilt linkage pivotally attached to the boom assembly and the bucket, and lifting means for raising and lowering the boom assemblyand the bucket, the improvement comprising: a pair of arms forming the boom assembly wherein the boom assembly includes a rearward boom arm and a forward boom arm pivotally connected together at respective ends; means connecting the lifting means with the forward boom arm; and sets .of alternately engageable and disen-gageable stop surfaces of which the surfaces of each set are respectively on the pivotally connected ends of the booms arms and cooperatively arranged so that as the lifting means raises the boom assembly the rearward boom arm is first raised to a predetermined position while one set of said stop surfaces remains engaged, after which the forward boom arm pivots relatively to the rearward boom arm to raise the bucket relative to the rearward boom arm until another set of the stop surfaces becomes engaged.

2. The loader linkage as described in claim 1 wherein there is a rear boom arm stop and said predetermined position is reached when the rearward boom arm contacts said rear boom stop.

3. The loader linkage as described in claim 1 wherein the tilt linkage includes a hydraulic cylinder which maini tains the bucket in a substantially level position as the boom assembly is being raised.

4. The loader linkage as described in claim 1 wherein the lifting means is a hydraulic cylinder which is pivotally connected at one end to the tractor and at the other end to the forward boom arm.

5. The loader linkage as described in claim 3 wherein the tilt linkage further includes a first link and a second link with the first link pivotally connected adjacent one end thereof to the forward boom arm and pivotally con nected adjacent the other end to one end of the second link, the other end of the second link being pivotally connected to the bucket; and the hydraulic tilt cylinder is pivotally connected at one end to the rearward boom arm and pivotally connected at the other end to a midportion of the of the first link to provide a hydraulically positioned tilt linkage which maintains the bucket in a substantially level position as the boom assembly is being raised.

6. A loader linkage for use with a tractor comprising; a rear boom arm pivotally connected at one end thereof to the tractor; a forward boom arm pivotally connected at one end thereof to the other end of the rear boom arm; a bucket pivotally connected to the other end of the forward boom arm; tilt linkage pivotally connected to the.

rear boom arm, the forward boom arm and the bucket; lifting means for raising and lowering the rear boom arm, the forward boom arm and the bucket; and a plurality of stop surfaces located at the connected ends of the rear boom arm and the forward boom arm to provide for limiting the pivotal movement between said rear boom arm and said forward boom arm when said lifting means is actuated.

7. The loader linkage as described in claim 6 wherein said plurality of stop surfaces include a rear boom arm upper stop surface, a rear boom arm lower stop surface, a forward boom arm upper stop surface and a forward boom arm lower stop surface, each of said stop surfaces so arranged that engagement of the two lower stop. surfaces determines the minimum angle between the rear boom arm and the forward boom arm, and engagement of the two upper stop surfaces determines the maximum angle between the rear boom arm and the forward boom arm.

No references cited.

HUGO O. SCHULZ, Primary Examiner. 

1. A LOADER LINKAGE FOR USE WITH A TRACTOR INCLUDING, A BOOM ASSEMBLY PIVOTALLY ATTACHED TO THE TRACTOR AT ONE END OF THE ASSEMBLY, A BUCKET PIVOTALLY ATTACHED TO THE BOOM ASSEMBLY AT THE OTHER END THEREOF, TILT LINKAGE PIVOTALLY ATTACHED TO THE BOOM ASSEMBLY AND THE BUCKET, AND LIFTING MEANS FOR RAISING AND LOWERING THE BOOM ASSEMBLY AND THE BUCKET, THE IMPROVEMENT COMPRISING: A PAIR OF ARMS FORMING THE BOOM ASSEMBLY WHEREIN THE BOOM ASSEMBLY INCLUDES A REARWARD BOOM ARM AND A FORWARD BOOM ARM PIVOTALLY CONNECTED TOGETHER AT RESPECTIVE ENDS; MEANS CONNECTING THE LIFTING MEANS WITH THE FORWARD BOOM ARM; AND SETS OF ALTERNATELY ENGAGEABLE AND DISENGAGEABLE STOP SURFACES OF WHICH THE SURFACES OF EACH SET ARE RESPECTIVELY ON THE PIVOTALLY CONNECTED ENDS OF THE BOOMS ARMS AND COOPERATIVELY ARRANGED SO THAT AS THE LIFTING MEANS RAISES THE BOOM ASSEMBLY THE REARWARD BOOM ARM IS FIRST RAISED TO A PREDETERMINED POSITION WHILE ONE SET OF SAID STOP SURFACES 